The correct option is B Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
Pectin is a heteropolysaccharide which is found in cell walls and intercellular tissues of certain terrestrial plants. It is a major component of middle lamella where it helps in binding the cells together. Therefore, the assertion is correct. Some cells in woody plants have a secondary wall and forms inside the primary wall. The cells start producing the secondary cell wall after the primary cell wall is complete and the cell has stopped expanding. Secondary cell wall provides extra support and protection to the cell and in turn strength and rigidity to the plant body. Hence, the reason is correct but not the correct explanation for given assertion. Therefore, option B is correct.